Question: $-7st - 6su + 3s - 1 = -3t + 1$ Solve for $s$.
Combine constant terms on the right. $-7st - 6su + 3s - {1} = -3t + {1}$ $-7st - 6su + 3s = -3t + {2}$ Notice that all the terms on the left-hand side of the equation have $s$ in them. $-7{s}t - 6{s}u + 3{s} = -3t + 2$ Factor out the $s$ ${s} \cdot \left( -7t - 6u + 3 \right) = -3t + 2$ Isolate the $s$ $s \cdot \left( -{7t - 6u + 3} \right) = -3t + 2$ $s = \dfrac{ -3t + 2 }{ -{7t - 6u + 3} }$ We can simplify this by multiplying the top and bottom by $-1$. $s= \dfrac{3t - 2}{7t + 6u - 3}$